A clinical test which could reliably predict an individual's future dental caries experience would permit a program for caries prevention to be designed to fit his needs. Presently documented caries activity tests do not directly measure the etiology of dental decay. The clinical evaluation of a caries activity test which measures the 1) quantity of formation and 2) the rate of acid production of dental plaque for each subject is proposed. Children 4 to 10 years of age will be selected who have no active carious lesions. Following the caries activity test they will be observed for two years. Clinical and radiographic examinations will be combined with retesting each six months. The caries activity test scores will be compared to the incidence of new carious lesions. A fluoride biopsy technique will be employed to determine how the enamel fluoride levels relate to the correlation between the test scores and the increments of caries lesions.